Mars, for example, has been traditionally considered the most likely area in outer space to contain some form of life due to its proximity to Earth, and due to evidence that shows that water has flowed on a large scale in Mars’ history (“Mars”, 2007; Conrad, 2007). The fact that water existed (Conrad, 2007) shows that at one point, Mars and Earth shared many things in common. Currently, water is known to flow on Mars in vapor and solid forms (Conrad, 2007), but it is unable to flow in liquid form on the surface (Conrad, 2007). It is most important to remember, however, the fundamental idea that bacteria and more complex organisms have been found in extreme environments in the past (“Panspermia”, 2007; Windows Team, 2002). These environments vary from deep into the earth’s rock crust, to the harsh cold of outer space, but, at the very least, the fact that bacteria or primitive cells can survive in these places is a solid supporter of extra-terrestrial life (“Panspermia”, 2007; Windows Team, 2002).
Scientists, by process of eliminating certain outer-spatial bodies due to certain characteristics prohibitive of allowing life to survive, have narrowed down the number of bodies where life could possibly survive to a small handful. Mars, as stated before, continues to be featured as one of the most likely destinations for extra-terrestrial life (“Life on Mars, 2007; Mars, 2007; Presszoom, 2007”). Albeit its reddish appearance and great, moonlike craters, Mars is often shown to have share many similarities with Earth (“Mars, 2007; Macey, 2007”). Aside from its proximity to Earth, Mars and Earth share similar rotational periods and seasonal cycles, and their volcanoes, valleys, polar ice caps, and deserts also are quite alike each other (“Mars”, 2007). Due to the water recently discovered on Mars, Mars has most definitely become the front-runner of all the other extra-terrestrial bodies to contain some life form (Conrad, 2007).
Europa, one of Jupiter’s moons, has also been named as a possible carrier of living organisms (“Europa”, 2007; Flowers, 2007). Some scientists believe that Europa contains an ocean under its icy surface (“Europa, 2007”; Flowers, 2007). This ocean may be a host of primitive life, as life has been proven to be able to exist in icy, brutal extremes (“Europa, 2007”). Europa’s subterranean ocean has been often compared to the Antarctic Lake Vostok (“Europa, 2007”).
Jupiter, the largest planet of the solar system, has also been subject to discussion about possible extra-terrestrial life existing (“Jupiter, 2007”). Famous for containing the enormous Red Spot, Jupiter is one of the four “gas giants” of the solar system. The 1953 Miller-Urey experiment that investigated possible life in outer space observed that a combination of lightning and the chemical compounds that existed in Earth’s early atmosphere could form the building blocks of life (“Jupiter, 2007”; Fox, 2007). The simulated atmosphere included water, methane, ammonia, and molecular hydrogen (“Jupiter, 2007”; Fox, 2007). All of these building blocks are currently found in Jupiter’s atmosphere (“Jupiter, 2007”; Fox, 2007). However, the article “Jupiter” counters that there is, in fact, only a small amount of water in the atmosphere, and that it would be very unlikely that Earth could carry Earth-like life. Possibly, of course, ammonia or water-based life might be able to survive (“Jupiter, 2007”). Ganymede, Callisto, and Titan are also considered options for places that could contain extra-terrestrial life. Ganymede has a magnetic field that might possibly be able to protect life from harmful radiation (“Ganymede, 2007”). Callisto has a salty ocean under its surface where microbial life could exist (“Callisto, 2007”). Titan also intrigues scientists for a number of reasons. The largest moon of Saturn, Titan has been believed to contain lakes or seas of methane, and its atmosphere is said to resemble the atmosphere of early Earth (“Titan, 2007”).
